This invention relates to a differential drive having a drivable differential carrier rotatably supported in a drive housing and comprising a carrier portion and two cover parts closing the ends of said carrier portion. Two axle shaft gears are coaxially rotatably supported in the differential carrier. The shaft gears are received in coaxial cylindrical bores in the carrier portion and are each connectable to an axle shaft. The differential carrier receives two sets of differential gears. Each set of differential gears has at least one differential gear, having tooth heads slidingly received in cylindrical bores in the carrier portion centered on axes parallel to the axis of the carrier portion. The teeth of each of the differential gears of the two sets engage the teeth of at least one differential gear of the other set. The cylindrical bores for the differential gears are in the form of through-bores in the carrier portion. The differential gears have toothed portions followed by spacing journals. The differential gears, by means of their ends, are at least indirectly axially supported in the differential carrier.
Differential drives of the above type are known from DE 40 13 200 A1, for example. For the purpose of simplifying the production of the differential carrier, the carrier portion is provided with through-bores with a constant diameter produced simply by broaching. To axially fix the differential gears in the through-bores, it has been proposed that the differential gears be extended beyond their toothed portions, by spacing journals. The differential gears approximately correspond to the length of the carrier portion. At the ends of the through-bores, the differential gears are supported on stop or closing means usually formed by covers which close the differential carrier at its axial ends. However, it is also possible to use simply designed stop discs or securing rings inserted directly into the through-bores.
DE 40 17 800 A1 describes differential drives of a similar type wherein the differential gears only cover part of the length of the carrier portion. The partial length corresponds to the length of the toothed portions of one of the axle shaft gears plus the length of a central toothed region to permit mutual engagement of the teeth of the differential gears of the two sets. In this embodiment, the differential gears are received in blind holes provided in the differential carrier so as to start alternately across the circumference from both axial ends of the carrier portion. The blind holes are closed directly by stop discs clamped in between the covers and the carrier portion.
A characteristic feature of the differential drives of the above type is that the differential gears are supported directly in the through-bores on their tooth heads. Due to the reaction forces between the axle shaft gears and the differential gears and between the differential gears of the different sets relative to one another, the supporting means generate a high degree of friction at the tooth heads. Thus a torque-dependent self-locking effect is generated. As engagement between the teeth of the differential gears of the two sets takes place along only part of their axial length between the respective toothed portions engaged with the two axle shaft gears, the load conditions along the length of the differential gears vary. Also, because the coaxial cylindrical bores for the axle shaft gears and the axis-parallel cylindrical bores for the differential gears are penetrating each other radially, the latter are inadequately supported in the differential carrier, against inwardly directed reaction forces.